Invert emulsions have been known for many years as sprays for controlling pests. Such emulsions are water-in-oil emulsions and are considered superior to conventional oil-in-water or solution sprays because of reduced drift, evaporation and volatilization of the sprays, particularly during aerial application, increased rain resistance, and improved penetration in the case of systemic pesticides.
An improved invert composition for pest treatment is disclosed in U.S. Pat. No. 3,479,176 and is a marked improvement over the prior art invert emulsions with respect to reduced drift, increased rain resistance and improved penetration. Such invert emulsions are commercially available under the trademark "BIVERT" and consist of an emulsifiable concentrate containing an oil such as petroleum distillate and fatty amine salts and fatty acids, but no pest control agent.
All such invert emulsions, however, do suffer from two major disadvantages; namely, too high a viscosity and droplets that are too large in size. The result is difficulty in utilizing such viscous emulsions with conventional spray equipment and in the case of large size droplets, large volumes are required to cover the pest infested target area. With the application of large volumes of pesticides applied to foliage, damage can be caused due to the toxic effect on the foliage by over-concentration of the emulsifiers and/or oil in the large droplets applied.
These and other problems of present invert emulsions are discussed in detail in a U.S.D.A. Forest Service General Technical report PNW-3 of 1973 entitled "Aerial Spray Adjuvants for Herbicidal Drift Control" by Gratkowski and Stewart.